Bimetallic backing for artificial teeth



1951 R. E. OMORROW BIMETALLIC BACKING FOR ARTIFICIAL TEETH Filed Dec. 6, 1949 Flllri'.

VIIIIIIIIIIIIIIIL rIIIIIIIIIIII/I/I grwwwtom 13055 E OMorrow ATTORNEY Patented Oct. 23, 1951 BIMETALLIC BAGKIN TEETH G FOR ARTIFICIAL Ross iMorrow, Columbus, Ohio, ass'ignor 'to The Columbus Dental 'Manufacturing Company, Columbus, Ohio, a corporation of Ohio Application December 6, 1949, Serial No. 131351 14 Claims. .1

This invention relates to back-ings for artificial teeth and refers, more particularly, to backings used in association with interchangeable "or replaceable artificial teeth or facings. Such interchangeable teeth or 'facings are commonly provided with mortises tor receiving 'complementally shaped terions provided on the back-ings whereby these mechanical parts co-act to form a com- ;plete tooth unit for use in dental bridgework, dentures and the like.

Heretofore the dental industry has fabricated backiiigs containing a variety of constituent-elemental metals. The precious metals, such as, gold, silver, platinum and palladium have been used in one percentage or another. Moreover, someof the non-precious metals,- such as, copper, nickel and zinc, have been used in combination with one or more -of the precious metals. The formulas of the constituent metals have varied in accordance with the requirements. For example, where a bridge was to be assembled by soldering an effort was made to produce an alloy for back-ings that would resist appreciable-oxidation and which alloy would be stable in the human saliva without any deleterious eiTect on the human health. Likewise where a casting process was used in association with such backings, "an e'fiort was made to produce an alloy that was resistant to the deleterious gases that are liberated from dental -investments commonly employed in such process, and likewise such alloys were designed to be stable during use in the human mouth.

To meet these requirements of processing and use a variety of com-positions have been made and marketed heretofore. Moreover, a variety of colors have been produced in the alloys of the .past, the color depending upon the constituent metals used and the quantity of each employed in the respective formula. The color of some of these alloys has enhanced the natural life-like appearance of the artificial teeth, whereas, the color of other alloys has detracted from the appearance.

All alloys, which serve the desiredend in the dental processes, should preferably possess adequate tensile strength, suitable hardness and a melting range sufliciently high to stand up satisfactorily under the temperatures employed in the soldering and casting processes,

.For sometime .past, the translucency of the porcelain material used in the composition of artificial teeth has been increased. Likewise 'the degree of the translucency has kept pace with that of porcelain in the manufacture of plastic teeth, particularly those teeth made up of methyl methacrylate (acrylics). This trend toward increased translucency in artificial teeth has come about through the professional and public desire for a more life-like appearance. It has to do largely with the esthetic values demanded in dentures, bridgework, jacket crowns and the like.

The observation that certain colors of alloys used for backings have beneficial or deleterious effects upon the esthetic appearance of artificial teeth, and that the integrity of certain adequate physical properties ought to be maintained has lead largely to the development of the present invention. For example, back-ings having a more or less silver or platinum color (composed com mor-rly of silver in the greatest percentage, gold and palladium in lesser percentages, and platimum in still lesser percentages) have proved to be encouragingly desirable in meeting the requirements for the physical properties through the dental processing and in use in the human mouth. However because of the color of such a backing, it has been observed that the esthetic values thereof :are often lowered, especially when used in combination with the modern translucent artificial teeth. Such silver or platinum colored backings are apt to adversely influence the shade of the porcelain or acrylic teeth to an objectionable degree when the artificial work is placed in the human mouth.

The pleasing and satisfactory results in dental restorations are largely dependent upon the degree to which the artificial teeth of the bridge or denture match or harmonize with the colors or shades of the natural teeth. It is understood that the shades 'of the natural teeth are rather weak, pale or pastel in the degree of the color intensity 'found therein, and this obtains for each of the various colors that may be detected. Certain rather minor ranges of hues of brown, yellow, blue, red, gray and the like are round to one degree or another in the teeth of a natural dentition. The artificial teeth must match or at least harmonize with these color hues. It should be understood that extraneous factors of influence on the ultimate degree of hue or shade (which alter the shade of the artificial teeth) may come iron-1 a number of sources, for example, in the instance of interchangeable iacings used .in combination with backings therefor, the selection of a particular color of dental cement can be used to advantage, whereas the wrong selection may presage failure to even the untrained eye and particularly to the trained or discriminating eye. It is virtually impossible for the manufacturer to teeth. For example, the white metal alloys (havt ing a silver or platinum color) may influence the shade of an artificial tooth, whereby, it may take on an undesirable grayish or greenish cast or like, when such a backing is used incombination with the modern translucent artificial teeth. Whereas, the use of gold colored alloys (of one intensity or another of a gold color) often times will overcome the objections and therebybe beneficial in the ultimate results of the restoration. he gold color may help enhance certain shades, "such as, yellow, brown, pink etc;, when such color influence is demanded. Moreover, the gold color may reduce the objectionable vividness of an undesirable blue cast, a gray cast, a greenish "castet; and thereby bring about the ultimate 'color of the artificialteeth of an artificial restoration to become harmonious with the natural dentition." I

:It is understood in the art that backings of "white metal color (per se) have been made and used; heretofore, and that backings in the range 'or a gold color (per se) have likewise been employed. It is also understood (as explained above) that the white colored alloys have certain intrinsic advantages, especially in the desired physical properties. "Moreover, the gold-colored metals have certain intrinsic advantages espe- 'cially in contributing to the life like shade harmbny. The white metals generally are lackingine'sthetics; the gold metals, while satisfying esthetic considerations, are lacking in the required physical properties. Gold-colored alloys, c'omposedexclusively of precious metals, have been observed to fall short in meeting the adeguate tensile strength, suitable hardness and a sufficiently high melting range. Of course, the addition of minor amounts of copper and/or nickel may increase these properties to a certain limited extent, yet such compositions become especially lacking in their resistance to the de- The white colored alloys, composed exclusively of precious metals, are perceptibly the better in meeting tests for the physical properties.

The present invention has to do with a laminated or bimetallic back, and 'a main object herein is to provide a single backing unit, or a plurality of such backing units, having the mechanical advantages contained in a white metal alloy coupled together with the esthetic attributes of the gold colored alloy, as complete or composite articles of manufacture.

7 'Another object is to provide a range of'con- "stituent elemental white metals, preferably taken from the precious metal group, in such proportion as to provide a white colored alloy that will meet "the needs of the art in respect to the required structuralframework of a backing unit.

Another object is to provide a range of constituent elemental metals, preferably of the prepious .metal group, in such proportion as to producea gold colored alloy that will meet the need ofthe art in respect to the esthetic values demanded in the art.

Still another object is to provide the white and gold colored alloys in a composite bimetallic backing unit, the two laminas united together, to serve the art as a single article of manufacture and thereby take-advantage of the best qualities of each of the colored alloys.

Still another object is to provide the gold colored lamina produced in a range of colors, by making use ofa range of compositions, that will react beneficially, from an esthetic standpoint to improve or enhance the hues of artificial teeth for harmonious use with natural tooth hues, when used in combination with the varying degrees of the modern translucent artificial teeth or with the varying degrees of older lesser translucent artificial teeth, whether such latter teeth "and former teeth are made of a porcelain materialor of a plastic composition. I

' The composition herein found most dependable for the white metal alloy is preferably composed of metals from the precious metal group, such as, goldfsilver, palladium and platinum. Moreover the gold colored alloy composition found to be most dependable is likewise composed of metals from the precious metal group, such as, gold, silver and platinum. The colors in these alloys are dependent, to an appreciable extent, on the amount of gold used in the formula, whereas, the desired physical properties are dependent, to a large degree, on the amounts of gold, silver, palladium and platinu and the proportions of each, used in making up the white colored alloy.

Heretofore, relative minor amounts of non-precious metals, such as, copper, nickel, zinc and the like, have been used in general to impart certain physical properties (increase hardness, tensile strength, flow of metal in the molten state, etc.) especially to the gold colored alloys, yet for the purpose of alloys used as backing for artificial teeth it is believed that any appreciable use of non-precious metals detracts from the desirable integrity in and during the dental processes. Appreciable amounts of these non-precious metals may unduly promote brittleness, oxidation, wear on the processing tools, lower resistance to liberated gases given off by the dental investment and the like. Of course the use of relative minor amounts of some of these nonprecious metals in combination with some of the metals of some of the precious metal group can have advantages in compositions for certain specialized work and can even be fairly satisfactory for use as backings.

A. In producing the white-colored alloy portion of this invention, the constituent metals from the precious metal group, consisting of gold, silver, palladium, platinum and the like are preferred. Such an alloy composition may range in amounts of from 20% to 30% gold, from 40% to 50% silver, from 20% to 30% palladium and from .5% to 8% platinum.

B. In producing the gold-colored alloy portion of this invention, the constituent metals from the precious metal group, consisting of gold, silver and platinum and the like are preferred. Such an alloy composition may range in amounts of from 47% to gold, from 18%to 45% silver and from 1% to 8% platinum.

In producing the white colored alloy, where copper and/0r nickel are used, it is preferred to incorporate either or both of them at the expense of one or all of the precious metals silver, palladium and/or" platinum. The preferred amaevv :-amounts for scopper ror mickel, when arsed singly, may' range from' l25% to 6% inscombinationmith thezprecious :me'tals named in paragraph .EAiHibOI/C- When copper and nickel are used in combination therewith, :ispref-erred'rto :employ their :com-

bined' amounts Within theirange lot from to 6%. The use of copper and nickel :in these amounts can increase the hardness :and/or the tensile strength :of theralloy but their effect may lower the resistance .of the :alloy "to withstand the gases liberatedfrom :"the dental investment in the casting process, especially, when rather high temperatures 101 rburn vrout :are -.emp"loyed ror where :prolongeri sheat ssoaking is required, tor

where *a combination :of both of these monditi-ons becomeznecessary. 1

In producing the gol'dooloredalloy where cop'- per and/or nickel are used, the preferred amounts thereofuare the "sameas recited in the preceding paragraph and they :are preferably employed:

with :the' :precious metals named'inparagraph B, gold, silver, and platinum. In this :usethey should be added at the expense of the silver and/or the platinum, primarily leaving the gold in adequate amounts to give the proper'color =influence. Since the gold :coloredw-alloy is present in thin section :in the present invention :for a 'ibimetallic backing, :and accordingly since it has "little to .do with the framework strength, the prime .cb'ject is to retain the gold color through the processing so that itwill'present the 'proper esthetic influence-inthe completed dental restoration. "Therefore, in :som instances and :for some requirements the amounts of copper Wand/or nickel may be stepped up over "the preferred amounts mentioned aboveand still be'found satisfactory for use in combination-with the'lartificial teeth across the varying degrees of 'itranshicency. The following examples are :giveni'in percent- .ages by weight of constituent elements and purely by way of illustration :vvithout @in any sense restricting this invention thereto.

' FOR COLORED Example 1 Emamplez 'Per cent Percent Gold 22 Gold '26 Silver 4'7 Silver 43 Palladium '27 Palladium '24 Platinum 4 Platinum 7 Example .3 Example 4 Per cent Per cent .Gold 20 Gold 22 Silver 47 Silver '40 Palladium '30 Palladium 30 Platinum 7r] Platinum 8 Emmple Per cent Gold 25 Silver 47 Palladium 127.5

Platinum .05

FOR GOLD COLORED ALLOY Example 6 Eazample '7 Per cent v Per cent Gold '70 Gold 59 Silver 28 Silver 35 Platinum 2 Platinum 6 Example .3

Per cent Gold Example 9 Where copper .antl/ornickel are used, the following exam-ples are likewise given by way of illustration and without limiting the invention thereto.

FOR WHITEGOLO' RED ALLOY Example 11 Example .12

Per cent Per cent Gold 22.0 Gold .W .l 22.0 Silver 46.5 Silver "47.0 Palladium 26:5 Palladium 25.0 Platimim 2.5 Platinum 2.0 Copper 2.5 Nickel 4.0

Example 1.3

Per cent Gold 22.0

I Silver 47.0 Palladium 26:5

Platinum 1.5

Copper 1.5 Nickel 1.5

1 FOR GOLD COLORED ALLOY Example 14 Example 15 Per cent Per cent Gold 68.0 Gold 72.0 40 Silver 265 Silver 24.5 Platinum 1.5 Platinum .r 1.0 Gopprer 4:0 Nickel 2.5

Emample 16 I Per cent Gold 69:0

Silver "25.0 Platinum "1.0 (Jopper 3.25 Nickel 1.75

Reference has been made under the objects "recited above, to the'white colored alloy as meeting'the needs of the art for the structural framework of-the completed back 'in'g'uni-t, and likewise reference has been made to the gold-colored alloy as meeting the esthet-ic values required. By forming a backing of two layers, one layer from the Whiteco-lored alloy and one layer from the go'ldcolored alloy, the inherent advantages of each metallic composition are combined into one and the same *sing'leunit.

It has been found most satisfactory to produce a backing Wherein'the white alloy lamina is proportionally much thicker than the gold alloy lamina. (It should 'be understood that the himetallic alloys are used to their best advantage the fiatmember of the backing, or the equivalent portion"of-any other design of backing, be cause it serves particular advantage in makingup the tenon portion-of thebackin'g. In fact, the tenon is preferably made exclusively of the white metal alloy, all of which will be better'understood when'the drawings are later referred to herein.) In such a construction the white colored alloy performs its function in. providing the %7 structuralframework for the unit backing and more effectually retains its desired physical properties in the processing and in the use thereof. Thereby the stresses, strains, overloads and wear are taken care of by the higher tensile strength and by the hardness. Further, such a construction provides (by virtue of its greater bulk) greater resistance to the destructive gases liberated from the dental investments and the complete unit thereby retains its integrity of composition. The-gold colored alloy, provides the desired esthetic effects by virtue of its position in the lamina and by virtue of its color.

In" producing such a backing the process or processes commonly known to the bimetallic art may be employed, wherein, for example, an ingot of the white colored alloy of .500 of an inch thickness is placed in apposition with an ingot of the gold colored alloy of, for example, .008 of an-inch thickness (the latter is much less in the proportional thickness) and the two ingots are united by heat. This is not unlike some of the weldingprocesses where pressures of varying degrees are used in combination with heat for effecting a union of the two ingots. The welded ingot is then processed through various steps, such as, rolling and annealing until the bimetallic unit has been reduced to the desired thickness. Then strip cutting and blanking operations, and the like, may be employed in production of manufacture to obtain the required varieties and assortment of backing sizes. The assorted sizes of blanks thus obtained may be further processed whereby indicia are frequently applied by stencilling thereon certain characters, such as, trademarks, size numbers and the like. Punch presses and riveting presses are also commonly used to mechanically assemble and fasten the tenon to the flat member of the completed backing.

Where any of the non-precious metals are included in either or both of the alloy compositions it may be advantageous or necessary to use a neutral atmosphere in association with heat to effectively bring about the proper welding union between the white colored alloy composition and the -gold colored alloy composition. In fact, a neutral atmosphere is often found advantageous when compositions of the precious metal groups are used and where welding thereof is desired. Nitrogen atmospheres have been found useful as well as certain controlled non-oxidizing atmosphere associated with the welding furnace. Likewise fluxes may be used to advantage under certain conditionsand in association with certain alloys.

To facilitate a clear understanding of the present invention reference may now be had to the accompanying drawings, wherein:

Fig. 1 is a perspective view disclosing a. block of white colored silver-predominating alloy used in forming a laminated sheet complying with the present invention; 7

Fig. 2 is a similar view disclosing a complemental gold-colored block which is used in association with the block in Fig.1 to form the backing sheet comprising the present invention;

Fig. 3 is a vertical sectional view taken through the white and gold blocks when placed in superposed relationship and subjected to the action of heat and pressure to effect an inseperable union therebetween;

Fig. 4 is a detail sectional view disclosing the step of passing the block between reducing rolls for the purpose of forming a laminated sheet embodying the invention;

Fig. 5 is a view inside elevation, partly in section, disclosing the operation of transversely severing the sheet to form backings for dental facings;

Fig. 6 is a perspective view of a finished dental backing formed in accordance with the present invention;

Fig. '7 is a perspective view of a tooth facing looking toward the lingual side thereof, and illustrating the construction of the facing which is complemental to that of Fig. 6; T

Fig. 8 is a vertical longitudinal sectional view taken through the facing and disclosing its operative position on an associated backing;

Fig. 9 is a transverse horizontal sectional view taken through the combined facing and backing on the plane indicated by the line 99 of 'Fig. 8.

Fig. 10 is a vertical sectional view disclosing a slightly modified form of my improved backing.

Referring to the drawings, there has been disclosed in Fig. 1 a block or slab ll] of a metal alloy which I refer to aspossessing white color and which may beformed to embody the compositions set forth in Examples 1-5 and 11-13 herein disclosed, or reasonable variations thereof. Pref.-

.erably the block or slab ingot of this white-colored alloy is formed to possess a thickness of the order of .500 of an inch, its width and length measurements vary in accordance with the demands of manufacturing equipment. The goldcolored block or ingot indicated at I I, which may be formed to embody the compositions set forth in Examples 6-10 and 14-46, possesses a thickness of approximately .008 of an inch. When the thickness of the white-colored ingot is that above given in len th and width, the two ingots are preferably of the same size.

As shown in Fig. 3, the two ingots may be placed in vertical superposed order with their side edges in relative registration and placed in a press indicated at l2. While in the press, the two slabs or ingots are heated so that their interfaces are united. The welded ingot is then passed through various manufacturing steps, such as, as shown in Fig. 4, bein passed between reducing rolls l3 until a bimetallic sheet or strip has been for ed of desired thickness. Strip cutting or blanking operations, such as that disclosed in Fig. 5, may be performed on the bimetallic sheet or strip to produce blanks in sizes suitable to form backings M for dental facings of the interchangeable type disclosed at IS in the drawings.

The labial side of the tooth facing is of usual form and the lingual side is provided in this instance with a shelf or shoulder 16 and a flat backing-engaging face 11. In this face, there is provided a longitudinal slot H! which communicates at its rear with a longitudinal post hole l9 whose diameter is greater than the width of the slot., It will also be noted that the post hole I9 is of greater length than the slot [8 and that the hole projects downwardly toward the incisal edge of the tooth for a desired distance below the bottom of the slot l8.

To receive a tooth facing of the interchangeable type above described and illustrated in the drawings, my improved laminated backing is formed with vertically spaced openings which receive rivet extensions 20 provided on a rib 22 and a post 23. These parts comprise the usual tenon which is received in the mortise of a tooth facing'cofnposed of the slot l8 and the hole'l9. The tenon embodying the rib 22 and the post acrea e ings.- Thus,my-improved:bimetallicbacking may be used in association with facings known in:the artas the flatback type, as depicted in Fig. 10.. These facings are highly translucent andhave their backings extending completely to. the:

incisal edge. It is believed that the backing of the; present invention is equally efiective when: used in connection with this type of facing, as itis when employed in connection with the shoulderedtype;

By this construction; a porcelain or'plas'tic facing constructed as described may 'bereadily positioned or removedfrom the composite back ing, after the manner of standard interchange-' able tooth construction; The specific design of' the interfitting mortise and' tenonparts of the" backing and facing elementsabove'described are" optional and subject to considerable variation and do not form per se an essential part of the present invention; since other equivalent'inter changeable" backingand facing elementsmay be utilized Within'-the-"scope of the presentdi's closures;

From the above: description; it will: be: readily/ seen that this: invention provides an article; of:

manufacture, in the formv of a: laminated bir' metallic backing, that meets a long-felt need: in. the. dental art. It will also be seen that the compositionof the alloys used herein will successfully;v meet. the physical properties requiredindenturemanufacture. Further,v it will be. seen that; the=4o or plastic and" whether' the" composition thereof is ofa translucent or lessertranslucentnature.

I claim:

1;. A laminated color-modifying metallic backing for the mounting of artificial tooth facings;

comprising two permanently bonded"'la'yersioff alloyed noble metals, one layer having a predominantly goldcoloration and being composed; ofsaid'metals' ihsub'st'antially the renewin proportions stated-byiweight: I a

Gold, ran'gingin amo'untsifrom .47 to 75%. Silver; ranging in amounts from 18% to 45%. Platinum,ranging in amounts from 1% to 8% the other of said layers, predominantly. whitezim coloration, being, vcomposed of the, following; metals in substantially the. following proportions;

stated by weight;

Gold, ranging'irramounts from '20 to 30% Silver; ranging'inamounts "fro'm*1'8'%' to 47 Platinum, rangingin amountsi'from' .5% .td8%

2. A..laminated..color-modifying metallic backing for the mounting ofartificial tooth facings,

comprising, twopermanently bended layers of Still" further, it will be seen that the 45 10 alloyed noble: r'netal.'s one layer having a pr'e dominantly gol'd coloration aridbeingcomposedi of said metals insubstantially the-renewing- 'prb' portions stated by weight:

Gold; ranging in-amountstrom 4 1% to 75% Silver, ranging. in amounts from: 18% to 45% Platinum, rangingin amounts 'from' 1% to 8% the other of sai'd"layers, 'predominantlywhitein colo'ra'tion'; being. composed" of the following metals in substantially the proportions stated by weight:

Gold ,ranging inlamounts tronr20% to: 30%. Silver, ranging-in: amountsifroml 181% to 4'7 Palladium, rangingin. amounts from '20 to -3'0 Platinum rangihg in amountsi from .5 to 8%:

the: two layers" being joined-- and formed i'n-t oea substantially flat and-unitary memberand-tenong means carriedby said member for anchoring interchangeable tooth facings thereon.

3. A laminatedcolor-controlling metallic backing, for receiving artificial-tooth facings, comprise ing: two permanently bonded layers. of: alloyed 4 noble, metals, one of said layers having a predominantly. gold coloration and the other of= said layers possessing a predominantly whitecolora tion, the two layers being joined and formed into afl'at member.

A-laminated-coloncontrollingmetallicebac 1-1 ing for receiving artificiaLtooth f acings comprisl ingztwo permanently bondedelayershof alloyedfi. noble metals, one. of said layers having a predominantly gold." coloration andtlie other of said layers possessing a predominantly white colora-*" tion, the twolayersbeing'joiried and formed ihtb'f a fiat member, and tenon means formed with's'a memberto provide a support for the mounting of a separable tooth facing on said backing. Y

5; A laminated color-controlling metallic back-- ing-zfor receiving artificial toothiacings, comprising: two permanently bonded layers of alloyed -v noble metals, one of said layers having a predominantly gold ooloration' and the other: of -said layers possessing a predominantly white co'lo'r-'a-= tion, thetwoilayersbeingijoined andlformed into a fiatimember,andltenonrmeansformed with said 6. A laminated color-co ritrollingmetallic back j ing for receiving artificial tooth facings, comprisin'g'z two permanently bonded layers of alloyed noble metals; one of'sai'd layers" having" a predominantly'gold"coloration'andtheotherof said.

layerspossessing'a predominantly white colora= tion, .the twollayersbeinge. joined and formedinto;

a flat member, vthe layerof; white colorationv- 60 'possessinga greater thickness vin the backing than two permanently bonded layers-ofalloyed-noble metals,. oneeof said .layers'being composed-of gold,"

silver and- .platinumand inwhiehgold is the predominatingelement, therebyimparting to s'aiizl' first layer a substantially gold color, the other of said layers beihg compo'sed' of the metals=goldis th'e predominating element; impa-rting to said second layer a-substantially silver- 01 white color? 82' A c'olonmodified metal-lie" back'ing fbr" the.

mounting! o f artificiab to'oth f aciiig's; comprising. two permanently united layers of alloyed noble 11 metals, one of said layers being composed of gold, silver, platinum and copper and in which gold is therpredominating element, thereby imparting to said first layer a substantially gold color, and the other of said layers being composed of the metals gold, silver, palladium, platinum and copper in which the element silver predominates by weight, thereby imparting to said second layer a substantially white or silver color.

1 9. A color-modified metallic backing for the mounting of artificial tooth facings, comprising: two permanently united layers of alloyed noble metals, one of said layers being composed of gold, silver, platinum and nickel and in which gold is the predominating element, thereby imparting to said first layer a substantially gold color, and the other of said layers being composed of the metals gold, silver, palladium, platinum and nickel in which the element silver predominates by weight, thereby imparting to said second layer a substantially white or silver color.

10. A laminated color-modified metallic backing for the mounting of artificial tooth facin s, comprising: two permanently united layers of alloyed noble metals, a first layer having a predominately gold coloration and being composed of said metals in substantially the following proportions given by weight:

Per cent Gold 70 Silver 28 Platinum 2 the second of said layers, predominately white in coloration, being composed of the following metals in substantially the proportions given by weight:

the two layers being joined and formed into a substantially flat and unitary member. 7 V

11. A laminated color-modified metallic backing for the mounting of artificial tooth facings,

comprising: two permanently united layers of alloyed noble metals, a first layer having a predominately gold coloration and being composed of said metals in substantially the following proportions given by weight: 7

Per cent Gold 59 Silver 35 Platinum 6 the second of said layers, predominately white in coloration, being composed of the following metals in substantially the proportions given by weight: I

. Per cent Gold 26 Silver 43 Palladium 24 Platinum 7 of' said metals msubstantially the following pro? portions given by weight:- ,7

' f Per cent Gold 7 68.0; Silver 26.5 Platinum 1.5 pper -0v the second of said layers, predominately white in coloration, being composed of the following metals in substantially the-proportions given by weight:

Per cent Gold 22.0 Silver 46.5 Palladium .265 Platinum 2.5 Copper 2.5

Per cent Gold 72.0 Silver 124.5 Platinum 1.0 Nickel 2.5

the second of said layers, predominately white in coloration, being composed of the following metals in substantially the proportions given by weight Per cent Gold 22.0 Silver .470 Palladium .0 Platinum 2.0 Nickel 4.0

the two layers being joined and formed into a substantially flat and unitary member.

14. A laminated color-modified metallic backing for the mounting of artificial tooth facings,

comprising: two permanently united layers of alloyed noble metals, a first layer having a predominately gold coloration and being composed of said metals in substantially the following proportions given by weight:

Per cent Gold 69.0 Silver 25.0 Platinum 1.0 Copper -325 Nickel 1.75

the second of said layers, predominately white in coloration, being composed of the following metals in substantially the proportions given by weight:

the two layers being joined and formed into a substantially flat and unitary member.

ROSS E. OMORROW. f 1

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 192,167 Huguenin June 19, 1877 646,764 Steele Apr. 3, 1900 937,284 Craft Oct. 19, 1909 Number Number Name Date Fahrenwald Mar. 11, 1919 Kingsbury Nov. 10, 1925 Nowack Feb. 6, 1934 FOREIGN PATENTS Country Date Great Britain Nov. 26, 1941 

